An igneous rock forms quickly. Which characteristics could the rock have.
A. Evidence of folding
B. Small sand grains
C. Large mineral crystals
D. Smooth, sharp texture
C. Large mineral crystals
The characteristics that an igneous rock formed quickly could have are:
C. Large mineral crystals - When molten rock cools rapidly, larger mineral crystals have less time to form, resulting in smaller crystals or even no visible crystals.
D. Smooth, sharp texture - Rapid cooling of molten rock prevents the crystals from growing, resulting in a smooth and sometimes glassy texture.
Thus, the correct choices are C and D.
To determine which characteristics could an igneous rock that forms quickly have, we need to understand how igneous rocks are formed and the relationship between the cooling rate and the rock's features.
Igneous rocks are formed from the cooling and solidification of molten material, either magma below the Earth's surface or lava when it reaches the Earth's surface. The rate of cooling can greatly influence the size of the mineral crystals and overall texture of the rock.
A. Evidence of folding: This characteristic is usually associated with sedimentary rocks, which are formed by the accumulation and compaction of sediment. Igneous rocks generally do not exhibit folding unless they have undergone subsequent deformation or metamorphic processes. Therefore, an igneous rock formed quickly would not typically have evidence of folding.
B. Small sand grains: This characteristic is typically associated with sedimentary rocks, specifically sandstone. Sedimentary rocks form from the accumulation and cementation of loose sediment, which can include sand grains. Igneous rocks originate from molten material rather than the accumulation of loose sediment, so small sand grains would not be a characteristic of an igneous rock formed quickly.
C. Large mineral crystals: When magma cools slowly beneath the Earth's surface, it allows sufficient time for the mineral crystals to grow larger. Igneous rocks formed quickly, such as volcanic rocks that cool rapidly on the Earth's surface, do not provide enough time for such growth. Therefore, large mineral crystals would not be a characteristic of an igneous rock formed quickly.
D. Smooth, sharp texture: Igneous rocks formed quickly typically display a smooth, glassy texture due to the rapid cooling that inhibits the growth of mineral crystals. This texture is commonly seen in volcanic rocks, like obsidian or basalt, which cool rapidly on the Earth's surface.
Therefore, the correct characteristic for an igneous rock formed quickly would be D, a smooth, sharp texture.